Before a young unknown named Jennifer Aniston entered the equation, Courteney Cox was originally cast as Rachel on Friends -- and Facts of Life star Nancy McKeon was set to play Monica, which Cox ultimately took on. The role of Chandler that eventually went to Matthew Perry was originally given to lesser-known actor Craig Bierko.

And, indeed, Friends almost wasn't Friends -- the NBC smash sitcom's original title was Six of One. "We thought [that title] was such a snore," former NBC exec Karey Burke says in the May Vanity Fair's "Oral History of Friends" story, as excerpted in Thursday's Page Six. "Some people thought the show was too Gen X, way too narrow."

Nancy McKeon as Joanne 'Jo' Polniaczek in the Facts of LifeNBC/NBCU Photo Bank

Before landing the Chandler role, Perry, 42, was originally set to star in a show called LAX 2194, about baggage handlers of the future. Debuting in 1994, Friends lasted for 10 seasons and became one of the most successful and beloved sitcoms ever, with each cast member (also including Lisa Kudrow, David Schwimmer and Matt LeBlanc) netting $1 million per episode for the final seasons.